Failed Inspection - High Nitrous Oxide

1986 volvo DL wagon, 4 cylinders --no idea what the engine size is.

Any suggestions on an inexpensive fix for this problem?

 

CA SMOG2?

High NOX implies lean mixture or too high temperature burning, at any rate.
I've had trouble with my '88 740GLT and my '93 Toyota on NOX. Replacing
the 02 sensors, general tune up (plugs, cap, rotor, oil change, air filter
change) _AND_ new cats got me under the limit for both cars. But just
barely.

Generally speaking the SMOG techs may have some suggestions. Take the car
to a good exhaust shop and ask them to test the cat - they'll put it on a
rack and check the temperature before and after the cat. IRRC the
temperature after the cat should be about 2x what it is just before. They
shouldn't charge you for this.

-K

 

Du a full tuneup - new air filter, check the mixture, the timing, etc.
That will get it as low as it's going to go without mechanical work.

Then... here's a sugegstion... may work, may not...

I had a 1979 Ford F250 truck that just barely didn't pass on the
first try. The tech told me to come back in a month and in the
meantime run at least four tanks of Shell premium gas through
it (35 gal per tank) plus a couple of bottles of fuel injector
cleaner (even though the truck has a 4-barrel carb).
I had been running cheap Arco regular exclusively.

It passed with a bit of room to spare.

YMMV

Mike

 

DO YOU LIVE IN JERSEY? MY 96 850 DID THE SAME THING, DIDNT DO A THING
TO IT RAN IT THRU AGAIN AND IT PASSED. ITS ALL A SCAM. KELLY

 

What's interesting in Illinois is that instead of actually testing
the emissions from the tail-pipe, they just do diagnostics via the
OBD-II connector.

Beverly

 

Those engines have an ignition system that "over advances" ignition
timing at part load. This is done in search of better fuel economy, but
ends up doing not much more than raising combustion temperatures which
causes NOx formation. On the windshield washer bottle is mounted the
ignition computer. Disconnect the vacuum hose and plug it, or if the
emission shop will get excited about a disconnected hose, put a ball
bearing inside the hose and put it back on. This will cause the timing
to run at the full throttle setting at all times, and I'll bet you won't
notice any fuel economy change.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

What if you have an older car such as mine with no OBD-II?

 

Just heard from a friend that a dealer in Marin has been having 3 brick
cats installed on older Volvos (with 2 brick cats) when they hit a car that
is in otherwise good shape but can't pass smog for high NOX.

I don't think you are alone on the high NOX problem.

-K

 

Mike,
I also have high nox problems ('83 245) and have been looking for a fix
to get it to pass (CA) smog.
There's an article on brickboard that describes what you're suggesting.
It talks about a "control unit transducer" and plugging a line to it. I
looked all over the net (and in my manual) and couldn't find a
picture/description of the unit so I could find it and plug the line...
If this is the same as the unit on the washer bottle, thanks for
identifying it! Is the vacuum line you refer to on the side of the unit,
toward the front of the car?
Now, on to my dilemma.
First time I had it smogged, it passed the pre test.
Took it two blocks over to the test station. The tech at the smog
station noticed this vacuum line disconnected, hooked it up and the car
failed. (pinging badly I might add)
I plugged the line and reconnected it and that causes the motor to ping
so much I'm afraid it's going to burn a piston. undrivable.
Why (if you know) would the motor run fine and pass smog with the line
disconnected and unplugged but rattle so much with it plugged?
I'm tempted to cut a hole in the line where it's not visible, just to
get it to pass.

 

What you're looking at is the correct thing.
The only thing I can think of is that you managed to trap a vacuum
inside the transducer, which would put the timing on impossible advance
at all times. As long as there's full ambient pressure trapped in there
you should be fine.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

Thanks Mike.
I thought about what if the plug leaked and pulled a vacuum in the
transducer then didn't let it equalize.
We'll try it again & check for a good seal...
What do you think about tossing 10% methanol in the tank for the test?

 

Methanol will help reduce combustion temperatures so it can't hurt.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

fwiw, after installing a plug (that didn't leak) all numbers fell to within
acceptable range and passed smog.
The tech (same guy had checked it for the past 8 years) scratched his head
when it passed quickly, without the usual pinging. He's no dummy, he knew what
was up. All he said was 'you're a smart guy...'
Can't say if mileage is affected, still haven't fixed the gear on the odo. I
don't drive it hard enough to tell if there is a performance hit.
It will run on regular or mid-range now instead of premium so that's cool.
Think I'll leave it plugged...
Thanks again Mike.
Clay